New OSU slug expert will help Oregon farmers combat the slimy pests

CORVALLIS, Ore. – Oregon farmers battling slugs in their fields will soon have a new ally in Rory McDonnell, a slug and snail expert who joins Oregon State University’s College of Agricultural Sciences this summer.

McDonnell comes from a research position at the University of California at Riverside, where he studies novel ways to control the troublesome mollusks. His position is new, one of several made possible by a $14 million legislative investment in research and Extension work based at OSU.

McDonnell plans to continue his studies on environmentally friendly slug control methods, including plant essential oils and biological control agents such as parasitoid flies and soil-dwelling nematode worms.

His appointment also includes an Extension component, so he’ll be partnering with Oregon farmers to try some of his methods in their fields.

Slugs are shell-less land-dwelling mollusks that crawl on their stomachs, and they're a chronic pest in Oregon’s farms and home gardens. The main culprit, said McDonnell, is the gray field slug (Deroceras reticulatum), a non-native species that was inadvertently brought into the U.S. from Europe.

The slimy critter causes extensive damage in grass seed fields, “but it also feeds on many other crops: brassicas, a wide range of other vegetables, fruits, clovers, hops and nursery plants,” McDonnell said. “In effect, it competes with us for food. Just about anything we grow, slugs love to feed on.”

Another molluscan pest, the European brown garden snail (Helix aspersa), infests nursery crops. The snail is a quarantine species in Oregon and California, which means plants shipped outside those states’ borders must be snail-free.

Poison bait is the mainstay of agricultural slug and snail control, McDonnell said, but it can be expensive to use over large acreages, especially if it doesn’t work—which happens often, he said. “So one aspect of my research has focused on identifying new attractants that could aid in trapping pest slugs.”

And yes, slugs do love beer—not the alcohol so much as the sugar and yeast, McDonnell said. “Research has shown that the water, sugar and yeast together do the trick.”

He is also investigating natural predators, including certain flies, some of them native to Oregon, that prey on slugs. Another potential natural enemy is nematodes, microscopic soil-dwelling worms. McDonnell is currently studying one that kills pest slugs and snails.

Developing more environmentally friendly control strategies, he said, will help not only farmers and gardeners but Oregon’s native slug and snail species, which are beneficial to the environment.

“The banana slug is one Northwest native species that most people would recognize,” McDonnell said. “Banana slugs perform important functions in forested ecosystems, helping to break down decomposing vegetation and return nutrients to the soil.”

A native of Ireland, McDonnell has a doctorate in environmental science and has worked to conserve native slugs and snails in his home country. He became fascinated with slugs as a child, when he learned that they have teeth sharper than those of sharks and can crawl unharmed over broken glass.

“I know slugs are not as attractive as butterflies or colorful beetles,” he said, “but I guess I just followed my passion. As a result, I am one of the few people in the world who works exclusively on slugs and snails.”

He will join the OSU faculty on July 16.

“This is a dream position for me,” he said. “Oregon is a great place to be a slug person.”

The Oregon legislature in 2015 allocated $14 million in additional funds to Oregon’s three statewide public services, all headquartered at OSU: the OSU Extension Service, Oregon Agricultural Experiment Station and Oregon Forest Research Laboratory.

The funding boosts a base budget of $118 million for 2015-16 and makes possible new research, development and outreach work in such areas as specialty seed breeding, seafood safety, rangeland ecology, juniper harvest and manufacturing, and community economic development.

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